Blue & silver lunar calendar poster (rrp £6)

These beautifully printed calendars show the exact shape of the Moon for each night of the
year, screenprinted in silvery metallic ink on a deep midnight blue
background. As well as dates and days of the week, the calendar gives
the exact times of the full, new and quarter moons, and the times when
the moon changes from one sign of the zodiac to the next. I've been
producing them since 1989. The posters measure 12 inches by 33 inches
(31cm x 84cm) (approx.), and are both lovely and useful!
Click here for prices and ordering information.

The date and time of the Sun’s movement into each zodiac sign is
printed at the bottom of the calendar - these of course include the
solstices and equinoxes (in March, June, September and December) - and
a key to the zodiac symbols is also given. When there’s a solar or
lunar eclipse, the type of eclipse and time of greatest eclipse are
shown instead of the full- or new-moon time, this being just a
few minutes different. (See the
FAQ
for why.) The moon’s phases are drawn for midnight, and the last one
shown in each month (for 24:00 GMT on the last day) is pictured again
at the top of the next month’s column.

All the times shown on the calendar are in Greenwich Mean
Time. It’s a “Northern-hemisphere” design, in the sense that the
shapes would appear back-to-front (or upside-down) in the Southern
hemisphere - though in any case the moon is usually seen with the
bright limb turned downwards, toward the horizon, the exact angle
depending both on your latitude and on the time of night. The
calendar is nevertheless useable anywhere in the world, since the
moon’s shape appears (almost exactly) the same wherever you are on
Earth.

A Southern-hemisphere version is also available, however
(pictured right), which shows all the shapes the other way up, and
uses New-Zealand standard time-zone (12 hours East of Greenwich).

The average time from one full moon to the next is approximately 29
days 12 hours and 44 minutes (a “synodic month”), which is almost a
whole day less than the average calendar month, and this is why the
pattern on the calendar slopes upwards to the right. This pattern
continues if you put calendars for successive years side-by-side.
Twelve lunar cycles - from new to full and back to new again, 12 times
- together take about 10.875 days less than one whole year (a year
being the time it takes for the Earth (along with the Moon) to orbit
the Sun, about 365.2425 days).

Seen from Earth, the moon always moves forwards through the zodiac (unlike the
planets, which sometimes appear to go backwards, or retrograde,
against the background of the “fixed stars”). She spends a bit more
than two whole days in each zodiac sign, completing the cycle through
all 12 signs in one “tropical month” of on average, 27 days 7 hours
and 43 minutes. The time when the moon moves into a zodiac sign from
the previous one - an “ingress” - is shown on the calendar by the
Zodiac symbol of the new sign, with the time printed next to it, using
the 24-hour clock.

The calendar uses the usual “tropical zodiac”, in which the Sun moves
into Aries on the Spring equinox each year. Some people (biodynamic
gardeners for example) are interested in the sidereal zodiac,
which corresponds instead to the constellations of stars seen in the
sky. The tropical and sidereal zodiacs coincided in AD 221
(allegedly), but due to the precession of the equinoxes, the tropical
zodiac has moved backwards relative to the sidereal one by nearly 25
degrees. The moon thus moves into any particular sidereal sign
about 1 day and 21 hours after moving into the same tropical
sign (the one shown on the calendar).